In a mobile communication system of an LIE (Long Term Evolution) scheme defined in the 3GPP, each mobile station UE is configured to transmit a transmission acknowledgement signal (SPS A/N) after a predetermined timing (e.g., four sub-frames) from the timing of receiving downlink data to a radio base station eNB via PUCCH (Physical Uplink Control Channel) with respect to the downlink data scheduled by semi-persistent scheduling (hereinafter, referred to as “SPS”) and transmitted via PDSCH (Physical Downlink Shared Channel, a downlink data channel).
However, since a method for assigning an SPS A/N transmission resource candidate to each mobile station UE has not been defined in the 3GPP, there is a problem that the SPS A/N transmission resource candidate may not be appropriately assigned in the above-mentioned mobile communication system.
Therefore, the present invention is intended to overcome the above-described problem. An object of the present invention is to provide a radio base station capable of appropriately assigning an SPS A/N transmission resource candidate, and a mobile communication method therefor.